Question

Find out the missing alphabet/ number.

3, 7, 15, 31, 63? 

Options

• 92

• 115

• 127

• 131

Answer 1

127

Explanation:

The series is moving as:

3 = 2² - 1

7 = 2³ - 1

15 = 2⁴ - 1

31 = 2⁵ - 1

63 = 2⁶ - 1

127 =2⁷ - 1